This invention relates to apparatus for delivering individual flexible web products, and more particularly it relates to a high speed delivery system for plastic bags and containers.
In the production of individual flexible web products such as plastic bags and containers, the bag stock is typically supplied in the form of a continuous web of thermoplastic material which has been folded upon itself to form two plies. In forming individual plastic bags and containers, portions of the thermoplastic material are severed from the web. These severed areas also become side seams for the bags because they are typically sealed at the same time as they are severed by the use of a heated wire element. The plastic bags are then stacked, counted, and packaged by packing equipment.
The severing and sealing operation typically takes place on a relatively large diameter rotating drum which may contain multiple heated wire severing and sealing elements positioned in grooves located within the outer periphery of the drum. See, for example, Tumminia's U.S. Pat. No. 4,369,449, assigned to the same asignee as the present inventors. As the drum rotates, different severing and sealing elements are actuated to raise them up to the drum surface to sever and seal a respective portion of the web of bag stock. The individual bags are retained on the drum by a vacuum arrangement as the drum rotates. Such drums are large and expensive pieces of equipment. However, they can presently be operated at production speeds in excess of the production speed of the packaging equipment.
Individual bags are then taken from the drum, stacked, and packaged. See, for example, Pat. Nos. Re 28,172, 3,254,889, 3,599,705, 3,640,050, and 3,842,568, for a description of typical stacking and packing apparatus. Desirably, the packaging operation occurs at the highest possible speed the equipment can be operated to increase productivity of the system. As shown in the above mentioned patents, presently, individuals bags are taken from the drum by a smaller drum, also suitably equipped with vacuum capabilities. The vacuum on the bags on the large drum is relieved at an appropriate point, and the bags fall onto the smaller drum where they are held in position by vacuum. At an appropriate point, the vacuum is released and the individual bags are pulled off the smaller drum by an orbital packer or similar device.
As is conventional, the orbital packing device is provided with a set of packer fingers which move in a circular path in precise timing with the smaller drum so that the fingers remove each successive bag from the drum and stack them. After a predetermined number of bags have been removed, count fingers or other suitable separation means are actuated to separate the continuous stream of individual bags into precounted stacks.
To accomplish this, the count fingers must move from a first position fully out of the stream of bags, to a second position fully in the stream. This movement must be accomplished in the fraction of a second between successive bags as they are delivered from the smaller drum. At high production rates, this time can be less than 0.1 seconds. This results in the production of tremendous acceleration forces on the count fingers as high as 30 times the force of gravity. High inertial forces also affect the remainder of the packaging system for the folding and loading of the product into dispensers. Thus, operation at the design limits of the packing equipment results in high inertial loading which is detrimental to machinery life and results in excessive downtime and maintenance costs.
Accordingly, it would be desirable to be able to utilize the capability of the product drum to produce products at the higher rates that it is capable of, and yet maintain or even increase the higher production rates without subjecting the packaging system to such high inertial forces. The need exists in the art for such a high speed delivery system.